Time base generator



Sept. 11, 1962 N. N. ESTES ETAL 3,054,031

TIME BASE GENERATOR Filed Nov. 28, 1958 INVENTORS. 2 NELSO/V IV. ESTES J MES J. MOORE.

United States Patent 5,054,031 TIME BASE GENERATGR Nelson N. Estes and James J. Moore, Austin, Tex., as-

signors to Union Carbide Corporation, a corporation of New York Filed Nov. 28, 1958, Ser. No. 777,011 3 Claims. (Cl. 317231) This invention relates to a time base generator, that is a device which generates a signal having a known desired relationship to time.

For certain applications it is desired to have a time base against which signals can be compared. For example, if it is desired to study a voltage or current as a function of time, a time base is necessary. Devices for producing time bases are referred to as time base generators. A time base generator can produce an output voltage or current which is any function of time, linear or exponential.

A family of electrochemical devices in which a number of different effects are achieved by the movement of ions in solution has recently attracted favorable attention. These devices have come to be known as solions. They are discussed in some detail in the literature: Journal of the Electrochemical Society, vol. 104, No. 12 (December 1957); Yale Scientific Magazine, vol. XXXII, No. 5 (February 1958) and Electronics Products Engineering Bulletin No. 1, published November 1957, by National Carbon Company, 30 East 42nd Street, New York 17, New York.

In application Ser. No. 717,676 filed February 26, 1958, by Richard N. Lane and James J. Moore reference is made to a particular type of solion referred to as an integrator. This device has the ability to indicate the integral of a current applied to it over a period of time. One type of integrator is provided with electrodes so that its signal can be read electrically; it is termed an electrical read-out integrator. The present invention employs such a device as its essential component; its construction and function will be explained below.

The principal object of the invention is the provision of a time base generator employing an electrical readout integrator, which generator is particularly adapted to the production of time bases of long duration. It will be discussed with reference to the accompanying drawing in which:

FIG. 1 is a circuit diagram of a time base generator embodying the invention; and

FIG. 2 is a diagram of a modified circuit.

The invention is a time base generator comprising the combination of an electrical readout integrator, a suitable current source, and a two-position switch. In one position the switch connects the current source to the input electrodes of the integrator (the input electrode and the common electrode) and in the other position disconnects the current source from the integrator. In the first position the switch connects a bias voltage between the common electrode and the readout electrode of the integrator and in the other position connects the bias voltage across the input electrode and readout electrode of the integrator to clear it.

The time base generator of the invention is capable of producing an output voltage or current which is any function of time, linear or exponential depending upon the input current. For a linear function, a constant current input is required. For an exponential function, an exponential input current is required. For the sake of conciseness, the invention will be described with particular reference to production of a linear time base.

An electrical readout integrator as the term is used herein is a solion consisting of a cell containing as electrolyte a solution of a reversible redox system, the solu- "ice tion being divided into three zones of different concentration of a measured species of such system, all zones being electrically connected through the electrolyte. One of the three zones is of variable concentration. It is called the integral zone. It is provided with two electrodes, one termed the Common electrode, or integrator anode, the other the Readout electrode, or integrator cathode. Another zone of concentration which is high in concentration of the measured species is referred to as a reservoir zone. It contains an electrode termed the Input or reservoir electrode. Separating the integral zone and the reservoir zone is a zone dilute in the measured species of the redox system. It is provided with an electrode called a Shield or scavenger electrode. 7

In operating an electrical readout integrator, a biasing voltage is applied across the common and readout electrodes, the common electrode being made the anode of the circuit, so as to furnish the readout current which is proportional to the concentration in the integral zone. A similar biasing voltage is applied across the shield and input electrodes, the latter being made the anode so as to maintain a high concentration of measured species in the reservoir zone and to clear the dilute zone of any ions of the measured species which may have escaped into it from the integral zone. With these electrodes biased as described, when a source of current is connected across the input electrode and the common electrode so that the latter is the anode, the concentration of the measured species of the redox system is increased in the integral zone. The increase can be read electrically on a suitable meter in the biasing circuit of the integral zone. When the current source is disconnected, the increased concentration of measured species is maintained in the integral zone by reason of the configuration and location of electrodes in that zone, and when the source is again connected, again an increase in concentration is noted. Thus, the device integrates the current applied over a period of time. When the bias voltage is applied between the input electrode and the readout electrode so as to make the input electrode positive with respect to the readout electrode, the iodine concentration in the integral zone is decreased and thus the integrator is cleared.

Referring now to FIG. 1 of the drawing, an electrical readout integrator E is diagrammatically represented. A biasing voltage is provided by a circuit including a battery B the voltage being applied between the input electrode 1 and the readout electrode R when a twoposition switch S is in one position (position 1 or clearing position) and between the common electrode C and the readout electrode R of the integrator when the switch S is in the other of its two positions (position 2 or integrating position). When the switch S is in the second position, the common electrode C is the anode of the biasing circuit, and when it is in the first position, the input electrode is the anode of the biasing circuit.

In the readout biasing circuit including the battery B a network including a negative temperature coelficient resistance 10 which is connected in parallel with a seriesconnected ammeter 12 and resistor 14- is provided. The purpose of this network is to maintain the slope of the time base output constant for a given input over a normal operating temperature range. A resistor is provided between the battery B and the common electrode C of the integrator E to prevent excessive fluctuation in the readout signal when the switch S is moved from position 1 to position 2.

A bias voltage is applied across the shield electrode S and the input electrode 1 of the integrator from a battery B The battery B is so connected as to make the input electrode I the anode of the circuit.

The constant current source which produces the input signal to the integrator E includes a battery B any one of a number of resistors 16, 18, 20 and a multi-position switch S When the switch S is in proper position (position 2), the constant current source is connected in series with the input electrodes of the integrator by connecting the switch S to the desired one of the resistors 16, 18, 20. The purpose of providing a plurality of resistors in the circuit is to provide for a plurality of time bases of different lengths. As many resistors may be provided as desired. When the switch S is in position 1, the constant current source is disconnected from the integrator.

The device illustrated by FIG. 1 is a linear device. By inserting a capacitor 22 of appropriate capacitance with regard to the battery B and the resistors 16, 18, 20 between the switch S and position 2 of switch S as shown in FIG. 2 a derivative time base is produced.

Illustrative of the invention, a time base generator embodying its principles was constructed in which the battery B and the battery B both had a voltage of 0.9 volt and the battery B had a voltage of 24 volts. The resistors 16, 18, 20 had resistances of 0.68 megohm, 6.8 megohms and 68 megohms respectively. The resistor 15 had a resistance of megohms.

Using an XY recorder of commercial manufacture with a sensitivity of 6 /3 microamperes per inch on the X axis linear time bases of 5 seconds per inch, 50 seconds per inch and 500 seconds per inch respectively were produced when resistors having the resistances just enumerated were connected to the integrator.

A full description of an electrical readout integrator suitable for use in the amplifier of the invention is found in the application of Nelson N. Estes, Ser. No. 777,009 filed concurrently herewith, now US. Patent No. 3,021,482, issued February 13, 1962.

We claim:

1. A time base generator comprising the combination of an electrical readout integrator, a source of input current, and a two-position switch, said electrical readout integrator being a solion consisting of a cell containing as electrolyte a solution of a reversible redox system, said solution being divided into three zones of different concentration of a measured species of such system, one of said zones being of variable concentration and having two electrodes, one termed the common electrode of said integrator, the other the readou electrode of said integrator, a second of said zones of concentration being high in concentration of said measured species of said reversible redox system and having an electrode termed the input electrode of said integrator, and the third of said zones being dilute in said measured species of said reversible redox system and having therein an electrode termed the shield electrode of said integrator, said integrator having a readout circuit including said readout electrode and said common electrode, said switch in one position connecting said current source to said input electrode and common electrode and a bias voltage between said common electrode and readout electrode of said integrator, and in the other position disconnecting said source and voltage therefrom and connecting said voltage to said input electrode and readout electrode of said integrator to clear the same.

2. A generator as defined by claim 1 in which a resistor having a negative temperature coefficient is connected in the readout circuit of said integrator.

3. A generator as defined by claim 1 in which said input current source is a constant current source.

References Cited in the file of this patent UNITED STATES PATENTS 2,033,465 Graham Mar. 10, 1936 2,685,025 Root July 27, 1954 2,890,414 Snavely June 9, 1959 

